This invention relates to burner control systems for fluid fuel burners and particularly, to gas burner control systems wherein, upon a call for heat, a pilot burner flame is established and a main burner is subsequently ignited by the pilot burner flame.
Due to the increasing need for conservation of energy, many different types of burner control systems which eliminate the conventional standing-pilot have been proposed. Among such proposed systems are some which retain the pilot burner but provide for ignition of the pilot burner only when there is a call for heat. Such systems thus retain the proven reliability of igniting a main burner with a pilot burner flame but eliminate the waste of gas inherent in a conventional standing-pilot system.
A safety requirement of those systems wherein the pilot burner is ignited only when there is a call for heat is that gas be allowed to flow to the main burner only when a pilot burner flame exists. When the means used to sense the pilot burner flame and respond to it is electronic, meeting this requirement is complicated by factors which tend to falsely indicate the existence of a pilot burner flame, such factors including failure of a circuit component, excessive dirt or humidity on the flame sensing probe, and false signals or noise introduced into the circuitry.